Tsunefumi Mizuno 1 Fermi_Diffuse_ASJ_2010Mar.ppt Fermi-LAT Study of Galactic Cosmic-Ray Distribution -- CRs in the Outer Galaxy -- Tsunefumi Mizuno Hiroshima

Tsunefumi Mizuno 1

Fermi_Diffuse_ASJ_2010Mar.ppt

Fermi-LAT Study of Fermi-LAT Study of Galactic Cosmic-Ray Galactic Cosmic-Ray

DistributionDistribution-- CRs in the Outer Galaxy ---- CRs in the Outer Galaxy --

Tsunefumi MizunoTsunefumi MizunoHiroshima Univ.Hiroshima Univ.

on behalf of the Fermi-LAT on behalf of the Fermi-LAT CollaborationCollaboration

ASJ 2010 Spring MeetingASJ 2010 Spring MeetingMarch 25, 2010, Hiroshima, JapanMarch 25, 2010, Hiroshima, Japan

Tsunefumi Mizuno 2

Fermi_Diffuse_ASJ_2010Mar.pptIntroduction Introduction Cosmic-Rays and Galactic Diffuse Gamma-RaysCosmic-Rays and Galactic Diffuse Gamma-Rays

A powerful probe to study CRs and ISM in distant locations

HE -rays are produced via interactions between cosmic-rays (CRs) and the interstellar medium (or the interstellar radiation field)

• ISM distribution => CRs• those “measured” CRs => ISM

Fermi-LAT (2008-present)2.4 sr, 30 MeV-300 GeV

Tsunefumi Mizuno 3


[1]: CR sources: SNRs, HESS unIDs (Katagiri et al., Hanabata et al.) [2]: ISM and possible CR sources: molecular clouds (Okumura et al., Sada et al.)

[3]: Galactic CRs: This talk (cf. Abdo et al. 2009, ApJ 703, 1249; Abdo et al. 2009, PL 103, 251101; Abdo et al. 2010, ApJ 710, 133)

LAT Study of the Galactic Diffuse EmissionLAT Study of the Galactic Diffuse Emission

Fermi-LAT all sky map (1yr)

Tsunefumi Mizuno 4


CR Distribution in Milky WayCR Distribution in Milky Way• CR distribution is a key to understand the CR origin and propagation

• ISM gas distribution is traced by radio surveys + Galactic rotation • Then, Fermi-LAT is able to map out CR distributions in Milky Way with unprecedented accuracy

• Detailed study of the outer Galaxy (2nd and 3rd quadrant) will be discussed.• Study of the whole Galaxy is in progress

Gal.Center

Inner Galaxy

OuterGalaxy

Tsunefumi Mizuno 5


CR Distribution in the Outer GalaxyCR Distribution in the Outer Galaxy(2(2ndnd Quadrant) Quadrant)

• CR distribution is a key to understand the CR origin and propagation


Gal.Center

OuterGalaxy

Inner Galaxy

Abdo et al. 2010 (ApJ 710, 133)Contact: L. Tibaldo, I. Grenier

R=8.8 kpc

R=10 kpc

R=14 kpc

Gould Belt

local arm

Perseus arm

outer arm

Tsunefumi Mizuno 6


CR Distribution in 2CR Distribution in 2ndnd Quadrant Quadrant

GALPROP prediction using PSR distribution as input sources

• The shape of CR spectrum in Gould Belt (d<=300 pc) is close to those measured at the Earth

Fermi data

• Decrease of CR densities with gradient flatter than expectations for SNR sources as traced by PSR

• Property of molecular clouds is also discussed in paper

pion-dacay

Bremsstrahlung

model (scaled)

200 MeV

-ray emissivity (per H-atom)

-ray intensity profile

Tsunefumi Mizuno 7


CR Distribution in the Outer GalaxyCR Distribution in the Outer Galaxy (3 (3rdrd Quadrant) Quadrant)

• CR distribution is a key to understand the CR origin and propagation


Gal.Center

OuterGalaxy

Inner Galaxy

R=16 kpc

R=12.5 kpc

R=10 kpc

outer arm

Perseus arm

inter arm

local arm

Tsunefumi Mizuno 8


CR Distribution in 3CR Distribution in 3rdrd Quadrant Quadrant

Prelimina

Preliminaryry

• Spectral shape agrees well with the model for the LIS, and no significant spectral shape variation is observed.• CR spectrum in Tp~1-100 GeV does not vary significantly in the region studied

• Consistent view of CR density gradient: Decrease of CR densities with gradient flatter than expectations by a conventional model

Prelimina

Preliminaryry

GALPROP prediction using SNR distribution (Case & Bhattacharya 1998)

Fermi data

-ray emissivity (per H-atom)

-ray intensity profile

Tsunefumi Mizuno 9


Possible Scenario of CR Density Possible Scenario of CR Density DistributionDistribution

Preliminar

Preliminar

yy

• We ran GALPROP to search a possible scenario to explain the flat CR density distribution obtained by the LAT

Large halo size is required to reproduce the LAT data Or, a flat source distribution in the outer Galaxy is required

• A larger halo size and/or a flatter CR source distribution than those by a conventional models are required• Other scenarios may also explain the observed profile (e.g., Evoli et al. 2008)

test of several halo sizes

test of a flat CR source distribution in R>Rbk

Zh = 1, 2, 4,10, 15, 20 kpc

Rbk = 10, 11, 12,13, 14, 15 kpc

Tsunefumi Mizuno 10


SummarySummary

Thank you for your attention!

• Diffuse gamma-ray emission is a powerful probe to study the CR (and matter) distribution in distant locations in our Galaxy• Extensive analysis by Fermi-LAT is in progress

CR sources (Katagiri et al., Hanabata et al.) individual GMCs (Okumura et al., Sada et al.) non-GeV-excess, mid/high-latitude region (local CRs) large scale analysis (CR distribution throughout the Galaxy)

• Detailed study of the outer Galaxy is discussed Flatter CR density gradient than a conventional model toward the outer Galaxy

Flat CR source distribution and/or a large CR halo is a possible scenario

Tsunefumi Mizuno 11


Backup SlidesBackup Slides

Tsunefumi Mizuno 12


CR Distribution in 3CR Distribution in 3rdrd Quadrant Quadrant

• Spectral shape agrees well with the model for the LIS, and no significant spectral shape variation is observed.• CR spectrum in Tp~1-100 GeV does not vary significantly in the region studied

Prelimina

Preliminaryry

Prelimina

Preliminaryry

Tsunefumi Mizuno 13


Fermi-LAT View of the 3rd QuadrantFermi-LAT View of the 3rd Quadrant• One of the best studied regions in -rays

Vela, Geminga, Crab and Orion A/B• Galactic plane between Vela and Geminga (green square) is ideal to study diffuse -rays and CRs.

small point source contamination, kinematically well-separated arms (local arm and Perseus arm)

Count Map (E>100 MeV)

Preliminary

Preliminary

Vela

Crab

Geminga

Orion A/B

Tsunefumi Mizuno 14


Construction of the ModelConstruction of the ModelLocal arm

+2 HI maps(profile fitting technique;

arXiv:0907.0312)

+

Local arm

+ 1 CO map + excess E(B-V) map (Grenier et al. 2005)+ IC map (galprop model) + point sources (11 month list)

I(E, l, b) = A(E)*HI(l,b) + B(E)*Wco(l,b) +others+point_sources

Preliminary

Preliminary

Perseus arm

• Fit -ray data with 8 maps + 15 point sources (11 month source list)• CR spectrum (-ray emissivity) is assumed to be uniform in each Galactocentric ring

Tsunefumi Mizuno 15

Fermi_Diffuse_ASJ_2010Mar.pptIntroduction Introduction Cosmic-Rays and Galactic Diffuse Gamma-RaysCosmic-Rays and Galactic Diffuse Gamma-Rays

e+-

X,γISM

diffusiondiffusion energy losses energy losses reaccelerationreacceleration convectionconvection etc.etc.

π0

synchrotron

bremssHESS

SNR SNR RX J1713-3946RX J1713-3946

B

Pulsar,-QSO

PPHeHeCNOCNO

Chandra, Suzaku, Radio telescopes

A powerful probe to study CRs and ISM in distant locations

HE -rays are produced via interactions between Galactic cosmic-rays (CRs) and the interstellar medium (or interstellar radiation field)

IC

ACTs and Fermi(see K. Hayashi’s talk)

gas

gas

ISRF

e+-

π+-

(CR accelerator) (Interstellar space) (Observer)

(GMC is one of the best target matter)

Pioneering theoretical works by Hayakawa (1952), Morrison (1958), etc.

Documents

Tsunefumi Mizuno 1 Fermi_Diffuse_ASJ_2010Mar.ppt Fermi-LAT Study of Galactic Cosmic-Ray Distribution -- CRs in the Outer Galaxy -- Tsunefumi Mizuno Hiroshima